Project Summary Despite being in contact with bacteria since antiquity, copper is broadly toxic to bacteria. However, current research is limited regarding the overarching mechanisms of this toxicity. Copper toxicity is seen in practice where copper surfaces and tools significantly reduce nosocomial infections. Furthermore, during host mediated nutritional immunity (sequestering essential metals while bombarding bacterial with toxic metals), macrophages kill engulfed targets using copper, which is tightly regulated within the host. Bacteria have a copper export system consisting of a repressor, a copper chaperone, and a copper exporter. In the R35 this diversity supplement proposal is attached to, we seek to understand how bacteria evolved to interact with toxic metals. At the center of these metallo-interactions is understanding how the copper repressor works at an atomic level to regulate the operon under different metal conditions. For this proposal, Ms. Sanchez-Rosario will be working with myself, and Dr. Joseph Alvin, an experienced crystallographer and postdoctoral fellow in my laboratory, to crystalize the Streptococcus pneumoniae copper repressor protein under apo, copper, and zinc conditions. Further, she will be determining how a sugar import system that we show is regulated by the copper repressor aids in overcoming copper stress.